1. Field of Invention
The invention pertains to a microfluidic system on chips and, in particular, to a partially closed microfluidic system in which the fluid makes a reciprocal motion and a corresponding fluid driving method.
2. Related Art
Pump systems are commonly used in driving fluid. In addition to the uses of external pumps, chips also employ internal driving methods. These built-in driving means can be classified as mechanic micropumps and non-mechanic micropumps. In particular, the mechanic micropump technique includes the reciprocating-diaphragm and peristaltic types.
Most existing micropumps belong to the reciprocating-diaphragm type. This type of micropumps generally has a structure comprised of a pump body, an actuator, and a check valve. Commonly used actuators are piezoelectric, electrostatic, and thermopneumatic. Examples of non-mechanic micropumps include bubble pumps, diffuser pumps, electrohydrodynamic pumps (EHD), injection type EHD pumps, non-injection type EHD pumps, electroosmosis/electrophoretic pumps, ultrasonic pumps, thermocapillary pumps, pneumatic pumps, and vacuum pumps.
Generally speaking, mechanic pumps only provide one-way driving and, therefore, often cannot satisfy the need for two-way driving. Non-mechanic pumps have different limitations, depending upon different designs. For example, the driving effect of the electroosmosis pump is only observable on a capillary with a diameter smaller than 50 μm. Furthermore, these on-chip pumps have to be manufactured using a MEMS (Micro-Electro-Mechanic System) procedure. Since the cost of this kind of manufacturing process is higher, it is not ideal to be implemented on dispensable chips with limited functions.
As the current medical technology has more urgent needs in chip detection, dispensable chips have become a mainstream under development. In view of the fact that current pump technologies cannot satisfy the needs, it is therefore desirable to find other simple driving method.